Another Westbury Seal 15cc

[doubletop]

Regarding the comments on measuring castings vs the drawings. Fusion has the neat feature that you can import canvases, jpeg images that can be scaled and rotated to align with a drawing and  compared. So here is an example

I drew up the manifold interpreting the drawings and making judgement calls where necessary. This was done before I remembered the canvas feature so hadn't imported one



Then I imported a copy of the drawing for comparison. Pretty close really, when you consider the necessary guesswork dimensions



Then I scanned the casting on the photo copier and thankfully all the critical bits lined up



So Fusion may be a neat way of determining how much you've got to play with on the castings and where the dodgy areas may be

Pete

[doubletop]

I have done a bit more Fusion by making a start on the internals. I think I am going to fabricate the camshaft and crankshaft as that worked well for me doing the Malcolm Stride engines (Lynx, Bobcat and my Puma variant) so I have spent some time working on those. That then led to the conrods, pistons and cylinder liners



The cams are not aligned on the shaft yet as I just wanted to check dimensional correctness. The conrods did pose a minor problem as with my guesstimates for those dimensions missing from the plans, they fouled the lower edge of the cylinder liners. Measuring the castings didn't help and getting the dimensions by inserting the plans as a canvas in Fusion the problem remained. I thinned them down until they didn't foul the liners. But if anyone has their own drawing for their conrods I would be grateful. Just as sanity check.

On the subject of conrods I noticed in Mikes (Vixen) thread

I contacted Kirk at Hemingways regarding the material for the Seal (and other) conrods.

He said; "For at least the past 30 years these have been made from HE15.  At launch (1940's), I believe they were supplied as gunmetal castings.  The patterns no longer exist…"

The conrods in my kit are bronze so maybe it is quite old. The aluminium castings are quite hard.



Some other thoughts. This problem with the manifold bolts fouling the cylinder head bolts. Only seven bolts go into the crankcase three are a problem (red) and the middle one is low enough to enable it and the cylinder head bolt to coexist. My plan for the two outer red bolts is only use them to fix the cover to the manifold and not to the crankcase. Five bolts should suffice. (thoughts please?)



Next step is to see if it would be possible to make a set of timing gears myself. I purchased a set of M0.8 involute cutters some time ago and they remain in their box. So I just now need to work out what is required to be able to make a stab at designing my own gears. That really is a case of starting from zero for me


Pete

[gadabout]

Yes the rods do clash with the liner , it’s mentioned in the “words and music “ I relieved the liner at the clash point.
My Seal also has the bronze rods, I bought an incomplete kit from eBay and bought the missing parts from Kirk including rings from him
Mark

[doubletop]

Yes the rods do clash with the liner , it’s mentioned in the “words and music “ I relieved the liner at the clash point.
My Seal also has the bronze rods, I bought an incomplete kit from eBay and bought the missing parts from Kirk including rings from him
Mark

Mark

I have been skimming through the "words and music" to make some sense of the drawings but I haven't really read them in depth as I will do that at the point of cutting metal. This exercise of redrawing the whole thing has helped a lot with the understanding and getting my head around how I am going to deal with things with my equipment. The fabricated cams and crankshaft being a case in point.

How did you find the bronze conrods? Mine look decidedly wonky, for want of a better word. Hopefully they will clean up and end up similar in weight. They aren't at the moment

I had a look at the timing gears today to see if I would be able to use my M0.8 involute cutters to make my own gears. Which will be something new for me. 16 and 32 tooth gears will work and come out very close the the original dimensions. The mounting point for the idler needs to be moved slightly and the cover still fits. The picture below shows the outline of the cover.



Notice the piston peaking over the top of the crankcase

Pete

[Jasonb]

If you are going upto the larger size gear teeth then just watch that you don't get too thin by the time the keyways have been cut. Come across this a lot with the crank gears on Hit & Miss engines where the shaft is quite large so you often have to go with a smaller tooth size to leave enough meat around the keyway.

0.8MOD is usually the substitute for 32DP not 40DP.

[doubletop]

If you are going upto the larger size gear teeth then just watch that you don't get too thin by the time the keyways have been cut. Come across this a lot with the crank gears on Hit & Miss engines where the shaft is quite large so you often have to go with a smaller tooth size to leave enough meat around the keyway.

0.8MOD is usually the substitute for 32DP not 40DP.

Jason

I am not planning to use a key I don't have the tools to cut the slot. I will pin it on the boss. I'm using M0.8 as  that is what I have

Pete

[gadabout]

I don’t remember having any issues with the rods for wonkiness, I didn’t check their weights though.
I bought my gears from Kirk , they were good
My pistons also popped out of the block, I cut relief pockets in the heads, I think I might have cut my head and valve pockets a bit bigger than I should have as the compression seems low, I am going to revisit that, I have a spare head to work with. I used 1/4 x 32spark plugs too I just couldn’t see how 3/8 plugs were going to work in the combustion chambers , worth checking when you are drawing the heads !
I do like your drawing work!
Mark

[doubletop]

I don’t remember having any issues with the rods for wonkiness, I didn’t check their weights though.
I bought my gears from Kirk , they were good
My pistons also popped out of the block, I cut relief pockets in the heads, I think I might have cut my head and valve pockets a bit bigger than I should have as the compression seems low, I am going to revisit that, I have a spare head to work with. I used 1/4 x 32spark plugs too I just couldn’t see how 3/8 plugs were going to work in the combustion chambers , worth checking when you are drawing the heads !
I do like your drawing work!
Mark

Mark

Thanks re the drawing work. I find it a lot more productive to do the drawings and work out how I am going to go about things rather than leaping in, cutting metal, and wishing I'd checked before hand. For example the clashing of the conrods. A bit of a problem to deal with if the cylinder liners have already been installed. My usual approach, once I do get started on making things, is to use my down time to think ahead a few stages and make sure I have things in order. That's why I have just jumped from looking at castings to looking at the gears. If I can't make them I need to get them on order so I have them ready when I'll need them. With that I am just off to the workshop for my first ever attempt at gear cutting.

(BTW the drawings do say 1/4" x40 but my kit came with 3 very old 1/4" x32 plugs)

Pete

[gadabout]

The bits of my seal I got from EBay had 3/8” plugs with it , I thought the ones you have might have been also.
Mark

[gadabout]

I’m just across the Tasman from you in Tasmania too!

Mark

[doubletop]

The bits of my seal I got from EBay had 3/8” plugs with it , I thought the ones you have might have been also.
Mark

Mark

Ah! that may explain why you would have thought 3/8" plugs were required.

Pete

[doubletop]

Well I had my first attempt at cutting gears. Something I had always wanted to do. My first attempt was the, in my case, 16 tooth crankshaft and idler gears in bronze as I had a short offcut. You will see that the outer end is a little undersized. The offcut was 14.44mm diameter and the blank needed to be 14.38mm. The initial skim was a tad too much.



Although my mill has CNC I don't have a 4th axis yet so I used the dividing plate in the rotary table to index the job.  The cuts done with the CNC and a small Gcode program. As this was my first attempt I cautiously only used 0.2mm steps in the depth of cut and a pretty slow cutting rate. As I was useing such light cuts I did not see the need for tailstock as it would just get in the way

Things went well until the last tooth and it was slightly oversize. I rarely use my dividing plates and had to search for the manual to remind myself how to use them. Looking for the cause of the oversized tooth I now find the requirement for 10 steps on the dividing plate isn't 10 holes it is 10 gaps and 11 holes.

Anyway encouraged by the result of the first attempt I'll try again and speed up the cutting rates.

Pete

[doubletop]

I’m just across the Tasman from you in Tasmania too!

Mark

 

[uuu]

You're not alone in miscounting the dividing head holes.  At my last visit to the club, the mill was set up for gear cutting = with a note asking that the set-up be left alone.  There on the table was a small gear, with one oversized tooth!

Wilf

[doubletop]

 

You're not alone in miscounting the dividing head holes.  At my last visit to the club, the mill was set up for gear cutting = with a note asking that the set-up be left alone.  There on the table was a small gear, with one oversized tooth!

Wilf

Wilf

I just accept these errors as part of the learning process, if everything worked first time you wouldn't learn much and always wonder what you had missed or had just been lucky on the day. 

I also wasn't happy with my method of setting the cutter height but since my first attempt I have found a method of doing it. We shall see tomorrow.

Pete